Many engine systems use high pressure unit injectors having two valves per injector (cylinder). The first valve is located in the pumping part of the injector and cooperates with the cam shaft and a pumping plunger to create high fuel pressures. This valve is commonly referred to as the pressure control valve. In certain engine systems it is also known as a spill control valve. The second valve controls fuel injection from the injector. This valve is known as the needle or injection control valve.
Depending on the engine configuration, the cam shaft may be mounted to the side of the cylinder block or alternatively it may be mounted above the cylinder block. The first configuration results in an injector where the two valves (pressure control and needle control valves) (and their associated hardware) are separated and located on different parts of the engine. FIGS. 1a, 1b and 2 show the various engine configurations and location of the injector valves.
FIGS. 1a and 1b show a schematic picture of an engine 1 where the cam shaft 2 is mounted to the side of the cylinder block 3. It can be seen that the injector part of the injector 5, which incorporates the needle control valve, is located on top of the cylinder block 3. The injector pump 7, which incorporates the pressure/spill control valve, is located to the side of the cylinder block 3.
The pressure control valve and needle control valve are connected via a high pressure fuel line 9.
An alternative engine arrangement is shown in FIG. 2 which is a sectional view of an injector with an overhead cam arrangement. In this case the cam 11 is mounted directly above the injector 13. As a consequence the pressure control valve 15 and needle control valve 17 are mounted within the same injector structure. In the arrangement of FIG. 2, the pressure control and needle control valves are connected by a supply passage within the body of the injector 13.
In the event of an injector failure within a fuel injected engine system it can be difficult to identify the nature and location of the fault within the engine system. If the injector malfunction is electrical in nature then the fault can generally be identified by the engine management system. However, if the fault is mechanical in nature then the engine management system may not see any difference in its electrical inputs and may therefore be unable to locate or identify a fault.
Failure to identify a fault correctly can lead to wasted time, effort and cost in a service and repair facility because, for example, both pressure control and needle control valves may need to be tested and/or replaced manually before a successful repair can be achieved. It can also be the case that different control valves have different repair procedures and so identifying the location and nature of a fault prior to the commencement of a repair process is highly desirable.
The present invention seeks to overcome or substantially mitigate the above mentioned problems and to provide an apparatus and method for determining the presence of faults within the fuel injection system of an engine.